One conventional communications method that uses multiple antennas is, for example, the communications method known as Multiple-Input Multiple-Out (MIMO). In multi-antenna communications, which is typically MIMO, data communication rate can be improved by modulating transmission data of a plurality of sequences and simultaneously transmitting the respective modulated signals from different antennas.
FIG. 73 illustrates one example of a configuration of a transmission device based on the Digital Video Broadcasting-Next Generation Handheld (DVB-NGH) standard, in a case where there are two transmitting antennas and two transmission modulated signals (transmission streams). This example is disclosed in Non Patent Literature (NPTL) 1. In the transmission device, data 003 encoded by encoder 002 is split into data 005A and data 005B by splitter 004. Data 005A is interleaved by interleaver 004A and mapped by mapper 006A. Similarly, data 005B is interleaved by interleaver 004B and mapped by mapper 006B. Weighting synthesizers 008A, 008B receive inputs of mapped signals 007A, 007B, and weighting synthesize these signals to generate weighting synthesized signals 009A, 016B. The phase of weighting synthesized signal 016B is then changed. Then, radio units 010A, 010B perform processing related to orthogonal frequency division multiplexing (OFDM) and processing such as frequency conversion and/or amplification, and transmit transmission signal 011A from antenna 012A and transmission signal 011B from antenna 012B.
Here, a method is conceivable in which, for example, nine phase change values are set in phase changer 017B, and phase change is performed in 9 regular periods.
In the example illustrated in FIG. 73, splitter 004 is configured to split the data, but when a multi-carrier transmission method is used, such as OFDM, when a specific rule is established for the arrangement of the symbols along the frequency axis to improve data reception quality in the reception device, it is possible to improve data reception quality by using a phase change method other than the above-described method.